Cyclic Codes
Mostrando 13-24 de 36 artigos, teses e dissertações.
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13. Computing the minimal distance of cyclic codes
We describe an algorithm that improves on the standard algorithm for computing the minimal distance of cyclic codes.
Computational & Applied Mathematics. Publicado em: 2005-12
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14. Codificadores homomorfos sobre grupos
: In the work we consider homomorphic convolutional encoders over groups, with finites states, by using the concepts from estension of groups. Following [2] we call such a group estension Scherier product. In the way, we call the homomorphic convolutional encoders over groups Schreier encoders, and the convolutional codes produced by these machines as Schrei
Publicado em: 1996
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15. Codigos de grupo comutativo
The construction of commutative group codes for the Gaussian channel is considered. The initial vector problem can be formulated in a similar fashion as it has been done for cyc1ic group codes. All subgroups of ( Z IND. 8 ) POT. L , L = 2,3, with order 2 POT. M where m = 6,9, have been tested and new optimal codes were obtained. They have better efficiency t
Publicado em: 1996
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16. Uma contribuição a classe dos codigos geometricamente uniformes
In this research we present extensions oí code constructions whose codes belong to the class oí geometrically uniíorm codes. We consider two characterizations oí signal sets matched to groups. The first characterization is derived írom a noncommutative group which is the semidirect product oí a commutative group by a cyclic group oí even order. The se
Publicado em: 1996
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17. Isolation of cDNA clones for genes exhibiting reduced expression after differentiation of murine teratocarcinoma stem cells.
In the absence of retinoic acid, PSA-G teratocarcinoma stem cells spontaneously differentiate at a moderate frequency into fibroblast-like cells. In the presence of retinoic acid and dibutyryl cyclic AMP, PSA-G stem cells differentiate into parietal endoderm cells. We prepared a cDNA library from undifferentiated PSA-G teratocarcinoma stem cells; this cDNA l
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18. A Drosophila CREB/CREM homolog encodes multiple isoforms, including a cyclic AMP-dependent protein kinase-responsive transcriptional activator and antagonist.
We have characterized a Drosophila gene that is a highly conserved homolog of the mammalian cyclic AMP (cAMP)-responsive transcription factors CREB and CREM. Uniquely among Drosophila genes characterized to date, it codes for a cAMP-responsive transcriptional activator. An alternatively spliced product of the same gene is a specific antagonist of cAMP-induci
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19. Regulation of ubiG gene expression in Escherichia coli.
To study the regulation of the expression in Escherichia coli of the ubiG gene, which codes for the last enzyme in the pathway of ubiquinone biosynthesis, a fusion between the ubiG and lacZ genes was constructed in vitro. The results showed that (i) the expression of the ubiG gene was higher under aerobic conditions than under anaerobic growth conditions, (i
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20. Mechanism of CRP-mediated cya suppression in Escherichia coli.
Escherichia coli strain NCR30 contains a cya lesion and a second-site cya suppressor mutation that lies in the crp gene. NCR30 shows a pleiotropic phenotypic reversion to the wild-type state in expressing many operons that require the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex for positive control. In vivo beta-galactosidase synthesis in NCR30 was
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21. Identification of two new genetically active regions associated with the osmZ locus of Escherichia coli: role in regulation of proU expression and mutagenic effect of cya, the structural gene for adenylate cyclase.
The Escherichia coli K-12 gene coding for the nucleoid-associated protein HNS was cloned together with 5.6 kb of downstream DNA in the vector pACYC184. The cloned DNA complemented a mutation in the osmZ locus of E. coli, which codes for HNS. However, the multicopy plasmid harboring the cloned sequence was found to be mutagenic and to produce at high frequenc
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22. Sequence elements in the Escherichia coli araFGH promoter.
The Escherichia coli araFGH operon codes for proteins involved in the L-arabinose high-affinity transport system. Transcriptional regulation of the operon was studied by creating point mutations and deletions in the control region cloned into a GalK expression vector. The transcription start site was confirmed by RNA sequencing of transcripts. The sequences
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23. Thermoactivation of a periplasmic heat-stable enterotoxin of Escherichia coli.
Strains of Escherichia coli that host a plasmid that codes for the heat-stable (ST) enterotoxin showed 160 times more extracellular enterotoxin than intracellular activity. However, when washed bacteria were sonicated and incubated at between 50 and 85 degrees C, an activity similar to that of the ST enterotoxin was detected. No such effect was present in st
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24. Determination of the gene sequence and the molecular structure of the enterococcal peptide antibiotic AS-48.
The structural gene of the enterococcal peptide antibiotic AS-48 (as-48) has been identified and cloned by using two degenerate 17-mer DNA oligonucleotides on the basis of the amino acid sequences of two peptides obtained by digestion of the antibiotic with Glu-C endoproteinase. That as-48 gene codes for a 105-amino-acid prepeptide, giving rise to a 70-amino